This work will examine uric acid transport mechanisms, primarily in the rabbit kidney, with the goal of clarifying mechanisms of action of uricosuric drugs. Physico-chemical characteristics of uric acid transport in spearated renal cortical tubules will be evaluated. The effects of numerous drugs on uric acid transport in this system will be studied. Kinetic studies will be undertaken to define mechanisms of drug inhibition of uptake. We also plan to study uric acid transport in other tissue preparations such as renal brush border membranes.